I think you're in the right ballpark. My buddy picked one up for 700$ that was used sparingly and looked like new. It already had a muffler mod as well.. Thing is a beast..
If it's as newish as it looks then $750 might be a little low, but not much. $825 might still be a decent price, and if he's patient then even $950 is conceivable. Asking $1250 is a Hail Mary pass attempt at getting someone to buy his mistake.
Too high, yupp. I'm becoming a fan of my 660, but I only have about $300 into it (lots of work, though).
I wouldn't call it a lot. Stories get blown way out of proportion. Here at my 2 local stealerships they haven't had any issues.
My dealer told me they are having issues with modules. I doubt its many. Until all the Mtronic saw don't run Pig Fat I don't want one.
The few fallers I've talked to say they're ok. Some run great and some just act weird from time to time with bogging. My dealer has sold 2. One to a logger and one to a farmer. One logging company asked them to order all the 660s they could get after trying it. I think they ended up with 3 new 660s a couple months back.